Species- and compound-specific dynamics of nonstructural carbohydrates toward the world’s upper distribution of vascular plants

Abstract

Nonstructural carbohydrates (NSC) are the crucial components of plant metabolism, and NSC dynamics provide essential information on plant carbon balance, which usually changes toward the distribution limits of plants. NSC have been extensively used to study the elevational limit in trees all around the world. For alpine herbs, which occupy vast areas beyond treelines, such investigations are still lacking. To assess whether carbon supply is a limiting factor for the upper distribution limits of alpine herbs, we studied NSC in belowground organs of 11 perennial species across their 4500–6000 m elevation ranges in the Western Himalayas at the peak of the growing season. We found a general elevational increase in total NSC within and across species. Studied alpine plants contain simple sugars and fructans as the main NSC and less so starch. Species- and compound-specific elevation patterns were found for different NSC compounds, suggesting a regulatory role of NSC in alpine herbs acclimation rather than a general accumulation of all NSC resulting from growth limitation. Similar to studies on treeline NSC dynamics, our study shows that reduced carbon supply is an unlikely cause of high-elevation range limits in herbs. Yet, the elevational NSC dynamics in alpine herbs still needs further exploration, with an emphasis on different compounds and their function in acclimatory metabolic processes, to clearly identify the key mechanisms determining plant range limits. • Nonstructural carbohydrates (NSC) shortage is not a cause of plant elevation limits • Total NSC in studied Himalayan plants generally increased with elevation. • Simple sugars and fructans predominate in plant belowground organs. • Individual types of NSC compounds suggest an active acclimation to elevation